Feuding among Iran's political blocs has broken into the open recently, even before official candidates are announced for June's election to replace President Mahmoud Ahmadinejad.

Although President Mahmoud Ahmadinejad is barred by term limits from running… ( Khalil Hamra / Associated…)

TEHRAN — Iran will stage its annual show of solidarity and defiance Sunday, a festive day of scripted rallies and fiery oratory marking the 34th anniversary of the Islamic Revolution and denouncing "satanic" Washington and its allies.

But with a pivotal presidential election approaching in June, the veneer of unity among Iran's diverse political blocs has been wearing thin as average Iranians struggle to cope with a withering, sanctions-driven economic crisis.

Even before official candidates have emerged, a nasty spate of preelection infighting has erupted, unveiling an unedifying display of name-calling and mudslinging.

Last week, Iranians witnessed the stunning public spectacle of President Mahmoud Ahmadinejad going before the parliament to play an apparently secretly taped video clip that, he alleged, exposed corrupt dealings by the powerful family of parliamentary Speaker Ali Larijani — the president's bitter rival and a possible candidate to succeed him.

Ahmadinejad called for an investigation, arguing that corruption and power grabs were undermining his authority at a time when "external" attacks on Iran were accelerating.

But the speaker was unmoved.

"You did not observe the dignity of the Islamic Republic," Larijani admonished the president before the assembled lawmakers, labeling him a blackmailer and dismissing him from the parliamentary chamber."Farewell."

Iran's supreme leader, Ayatollah Ali Khamenei, has denounced the pre-electoral bickering as immoral and called on the squabbling parties to put away the long knives. The politicians say their bickering doesn't detract from their devotion to the supreme leader or the interests of Islam and the nation.

But many observers predict an escalation of hostilities as the election approaches.

"This is the opening salvo on the conflict surrounding the election," said Alireza Nader, senior policy analyst with the Rand Corp. "They are tearing the system apart."

Authorities in Tehran want to ensure that this year's election is not a repeat of the tumultuous 2009 balloting, which resulted in allegations of vote-rigging and mass street protests that shook the Islamic Republic. No substantial debate is expected on fundamental foreign policy matters, such as Iran's relations with the United States and Israel or the nation's controversial nuclear program.

Already, the government has arrested more than a dozen journalists in a pointed preelection media crackdown. But, as last week's parliamentary session showed, political acrimony within the confines of what is permissible can be substantial.

At the center of the turmoil is Ahmadinejad, reelected in the disputed balloting four years ago with the help of the conservative bloc loyal to the supreme leader. Under term limits, he cannot run again.

In recent years, Ahmadinejad has seen his prestige and popularity plummet as the economy has tanked and his abrasive style has cost him support with various Iranian power blocs, including former allies such as the Revolutionary Guard and many members of the clergy.

Among other setbacks, Ahmadinejad has seen more than half a dozen of his government ministers impeached, his power diluted and his top media advisor thrown in jail for publishing material deemed insulting to Islam and to the supreme leader.

Another Ahmadinejad ally was jailed for two days last week after the videotape expose. The president denounced the arrest as "ugly," and the aide was soon sprung.

Though he is leaving office in a few months, Ahmadinejad clearly wants to remain a player in Iranian politics. His populist social welfare policies have ensured a base of support among the poor.

This time around, though, the conservatives have made it clear that they want Ahmadinejad and his allies out. Khamenei appears to have turned on his onetime protege and is reported to prefer a chief executive more pliant to his wishes.

Nonetheless, Ahmadinejad is said to be pushing the candidacy of Esfandiar Rahim Mashaei, a chief lieutenant and political confidant who has also clashed with the clerical leadership. However, it is unclear if Mashaei, or any Ahmadinejad aide, would pass muster with the powerful Guardian Council, a hard-line panel of jurists and Islamic experts whose duties include vetting candidates.

Officially, candidates do not register until May for the election. But low-key electioneering, such as speeches in mosques and in public venues, is expected to begin shortly.

Speculation about who may seek the presidency has been rife. Along with Larijani, the long list of prospective candidates includes Ali Akbar Velayati, a former foreign minister close to the supreme leader; Mohammad Reza Aref, a former vice president; Hassan Khomeini, a cleric and grandson of the late Ayatollah Ruhollah Khomeini, founder of the Islamic Republic; and Mohsen Rezai, former head of the Revolutionary Guard and a candidate four years ago.

As the election nears, interest in the balloting appears lukewarm at best. Many Iranians seem preoccupied with pocketbook issues as the economy continues to stumble under the weight of evermore stringent foreign sanctions imposed in response to the nation's nuclear program, which the U.S. and others believe is designed to develop weapons, though Tehran says its goals are peaceful. Several people interviewed in Tehran suggested that their preference was a candidate who could help stabilize prices.

"For my husband and me, our main concern is who can slow the rise in prices and bring some stability to our economic life," said Farahnaz, 53, who was lugging grocery bags in the capital and declined to give her last name. "We would like our two sons to find decent jobs and be able to improve our purchasing power."